Many conventional transport aircraft have wing-mounted engines. One such aircraft is illustrated in FIG. 1, which shows a schematic, top isometric view of a conventional jet transport aircraft 100 with a wing-mounted engine 106. The aircraft 100 includes a fuselage 102 and a wing 104 extending outwardly from the fuselage 102. The engine 106 is housed in a nacelle 108 and is structurally attached to the wing 104 with an engine pylon or engine strut 110 (shown schematically). An aerodynamic fairing 109 extends between the wing 104 and the nacelle 108 and encloses the engine strut 110.
FIG. 2 is an enlarged, cutaway isometric view of a portion of the wing 104 of FIG. 1. The fairing 109 (FIG. 1) has been omitted from FIG. 2 for purposes of illustrating certain aspects of an engine support system 214 configured in accordance with the prior art. The support system 214 includes an inboard pitch load fitting 221a and an outboard pitch load fitting 221b fixedly attached to a front spar 211 of the wing 104 in a side-by-side clevis-type arrangement. The support system 214 further includes an inboard side load fitting 224a, an outboard side load fitting 224b, a center side load fitting 225, and a lower pitch load fitting 222. The side load fittings 224 are spaced apart from each other and fixedly attached to the front spar 211 and a lower wing skin portion 205 extending between the front spar 211 and a rear spar 212. The center side load fitting 225 is fixedly attached to the front spar 211 between the two side load fittings 224. The lower pitch load fitting 222 is positioned on the lower wing skin portion 205 aft of the center side load fitting 225 and is fixedly attached to at least one wing rib 227 extending between the front spar 211 and the rear spar 212.
An inboard side load clevis 234a and an outboard side load clevis 234b pivotally connect an aft portion of the engine strut 110 (shown schematically) to the inboard side load fitting 224a and the outboard side load fitting 224b, respectively. Additionally, two side load links 236 extend between the aft portion of the engine strut 110 and the center side load fitting 225. An upper pitch strut 231 extends forward from the pitch load fittings 221 and is coupled to a forward portion of the engine strut 110. A lower pitch strut 232 similarly extends forward from the lower pitch load fitting 222 and is coupled to a lower-aft portion of the engine strut 110.
The engine 106 transmits primary structural loads in flight as a result of its weight and propulsive capability. These primary loads can include pitch loads PL acting about a lateral axis 241, and side loads SL acting along the lateral axis 241. In general, the pitch loads PL are transferred to the wing 104 by the combination of the upper pitch strut 231 and the lower pitch strut 232. The side loads SL from the engine 106 are typically transferred to the wing 104 by the side load fittings 224 and the center side load fitting 225. The two pitch struts 231, 232 together with the two side load fittings 224 provide a measure of redundancy; if one of the two pitch struts or a related joint fails, the other pitch strut can adequately carry the pitch load PL from the engine 106 to the wing 104.
Manufacturing the prior art engine support system 214 described above can be a time consuming and costly process. Each of the separate load fittings (i.e., the pitch load fittings 221, 222; the side load fittings 224; and the center side load fitting 225) must be precisely located relative to the others to accommodate interchangeability between different engine struts as engines are changed-out for servicing, etc. A typical method for locating these fittings with sufficient accuracy involves positioning the bare fittings on the wing 104 with an elaborate tooling fixture during build-up of the wing. After the fittings are fixed in position, the various attach points are align-bored to ensure adequate alignment. Bearings are then installed into each of the finished bores. Not only is the tooling for these operations expensive, but the additional time required to install these fittings can add significant cost to the manufacturing process of the wing.